The Republicans can hold onto the 2016 election sea change by opening up to black voters and emphasizing loyalty to country over differences.

So Donald Trump was elected because of a political sea change. The question is, will it last, or even expand? Or was it a flash in the pan? Former president Barack Obama, after all, thought he’d put together a coalition that would outlast him, only to have former Obama voters turn to Trump to make the New York real estate mogul our next president.

But how did that happen? Most of the national pundit class has tried to explain the rise of Trump voters by pointing to racism, or economic resentment, or racism, or cultural change, or even, you know, racism as an explanation.

But Salena Zito and Brad Todd tried something different: They went to those voters and asked them. Their new book, out this week, is The Great Revolt: Inside The Populist Coalition Reshaping American Politics. And in writing that book, they asked swing voters why they voted for Trump in two ways: Face to face, in a series of deep and sensitive interviews, and en masse in a large opinion survey. Both inquiries produced a lot of useful material that both Democrats and Republicans would be well advised to study and internalize.

And the racism theory doesn’t hold up. After all, these are people who voted for Obama twice, then turned to Trump over a white woman. As one blue-collar voter explained to them: “I was born and raised Democrat. You didn’t talk Republican in my parents’ household. They were very strict and I figured I just continued the tradition and voted Democrat all of my life.”

That includes voting for Barack Obama twice. But he was disappointed. “It’s just that things got progressively worse and with Obama’s second term, instead of being a ... How can you say it? Instead of being someone who does a job, he was someone pussyfooting around ... That’s what turned me off ... I really wanted him to live up to those speeches he gave. They were perfect.”

His conclusion: “I wanted Barack Obama to succeed. He ended up hurting us. He was weak.” Trump, he feels is strong, and does what he says he’ll do.

The Great Revolt is full of interviews like this: People who supported Obama, but felt that the country was going downhill under Democrats and that Hillary would worsen that tendency, while Trump offered a chance to turn things around.

But as I read the book, another interesting thing leaped out at me: The role of social pressure. Trump did badly among college educated voters in places where there were lots of college educated voters, but he did well among college educated voters who lived in places that were more diverse. As Zito and Todd write:

Simply put, Americans who live their lives among a group of friends and neighbors with varied educational backgrounds preferred Trump more than Clinton or Romney, while college-educated Americans who live exclusively among other degree holders were less likely to support Trump, even if they were otherwise Republican.

Trump’s performance among college-educated voters who live in counties below the national average in education levels was right on the republican par — particularly in midsize and smaller counties in the Great Lakes swing states that determined the outcome of the election.

These voters did not face the kind of social pressure to oppose the lewd and coarse Trump that their college-educated peers did in the suburbs.

That makes sense, and it reminded me of an NPR story last week about how black voters face tremendous social pressure from other blacks to vote for Democrats:“What ... researchers found in a recent study is that social pressure from other black people is how this Democratic norm gets policed. They found that the expectations around this norm were so powerful that simply having a black questioner ask a black respondent about their voting preferences made that respondent more likely to say they were voting for a Democratic candidate ... So Kanye isn't wrong when he says there is a lot of social pressure for black people to vote Democratic.”

Nope. But there was a lot of pressure for traditional blue-collar Democrats to vote Democratic too. Last election, a lot of them flipped anyway, after concluding that the Democratic Party — now more interested in sexual minorities, celebrities, and recent immigrants than its traditional labor constituency — could no longer be trusted.

Will a significant number of black voters flip to the GOP in the same way? If they do, it’s a real problem for the Democrats. But to make that happen, the GOP will have to make black voters feel welcome.

How can they do that? In his inauguration speech, Trump offered the path when he said: “At the bedrock of our politics will be a total allegiance to the United States of America, and through our loyalty to our country, we will rediscover our loyalty to each other. When you open your heart to patriotism, there is no room for prejudice.”

Focusing on our common citizenship, a shared Americanness that transcends lesser differences is an attractive path, and it could be a winning path as well. If so, we may see a genuine sea change indeed.